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용접 띠철근 보강된 콘크리트 기둥의 역학적 거동에 관한 실험적 연구
최창식,Choi, Chang-Sik,Saatcioglu, Murat 한국콘크리트학회 1999 콘크리트학회지 Vol.11 No.2
지진다발 지역에서는 철근콘크리트 기둥의 단면을 합리적으로 구속함과 동시에 횡보강 띠철근의 세심한 배근등이 요구된다. 이러한 요구조건을 만족시키기 위한 보편적인 횡보강근 사용의 문제점으로는 높은 체적비(high volumetric ratio), 조밀한 간격(close spacings), 겹침(overlapping of hoops), 구부림(bends), 구부림 연장 (bend extensions), 시공상의 어려움과 콘크리트 타설상의 문제 등이다. 이러한 문제점을 해결하기 위한 한 방법으로는 요구되는 횡보강근의 체적비, 배역, 크기 등에 따라 이를 기조립, 용접하여 사용하는 것이다. 용접된 횡보강근의 사용은 겹침과 구부림, 구부림의 연장 등이 필요하지 않기 때문에 조립이 간편하고, 축방향 철근의 지지에 적합한 치수의 정확성과 재료를 절감시킬 수 있다. 더우기, 단면 내 횡보강 철근의 간격이 조밀해짐으로써, 코아 콘크리트 주변의 구속력을 균등히 분배시키게 되고, 이에 따라 코아 콘크리트의 거동을 향상시키는 결과를 얻을 수가 있다. 이에 본 연구에서는 이러한 용접 띠철근으로 보강된 철근콘크리트 기둥의 역학적 거동을 실험적으로 규명함과 동시에 철근콘크리트 기둥의 내진성능 향상을 위한 기초자료를 제공하고자 하였다. 그 결과 횡보강근의 강도와 연성에 영향을 미치지 않도록 용접됨과 동시에 충분한 신률을 가진다면, 용접된 격자형 횡보강근은 기둥의 띠철근으로써 사용가능한 것으로 판단된다. 특히, 용접된 격자형 횡보강근이 유효하게 거동하기 위하여는 1) 용접된 접합부위의 강도가 보강근의 모재강도 이상 2) 신률이 4% 이상이어야 할 필요가 있다. An experimental investigation was conducted to study the structural behavior of concrete columns confined with welded grids. The full-scale columns with different volumetric ratio, spacing and arrangement of welded reinforcement grids were tested under simulated seismic loading. The columns were subjected to constant axial compression of approximately 20% or 40% of their capacities accompanied by incrementally increasing lateral deformation reversals. The results indicate that the welded reinforcement grid can be used effectively as confinement reinforcement provided that the steel used, have sufficient ductility and the welding process employed does not alter the strength and elongation characteristics of steel. The grids improved the structural performance of columns, which developed lateral drift ratios in excess of 3% with the spacing and volumetric ratio of transverse reinforcement similar to those required by the ACI 318-95 Building Code. Drift capacity further increased when grids with larger number of cells were used. Furthermore, the use of grids reduced congesting of reinforcement while the dimensional accuracy provided perfect support to longitudinal reinforcement.
Screen Printing법을 이용한 반사방지막 제조
최창식,남정식,이지선,전대우,이영진,배현,김진호,Choi, Chang-Sik,Nam, Jeong-Sic,Lee, Ji-Sun,Jeon, Dae-Woo,Lee, Young-jin,Bae, Hyun,Kim, Jin-Ho 한국재료학회 2018 한국재료학회지 Vol.28 No.12
Anti-reflection thin films are fabricated on glass substrates using the screen printing method. Tetra ethyl silicate(TEOS) and methyl tri methoxy silane(MTMS) are used as starting materials and buthyl carbitol acetate(BCA) and buthyl cellusolve(BC) are mixed to improve the viscosity of the solution. Anti-reflection thin films are fabricated according to the number of the screen mesh and the characteristics improve as the mesh size increases. The transmittance and reflectance of the coated thin film using 325 mesh are about 94 % and 0.43 % in the visible wavelength. The thickness and refractive index of the AR thin film are 107 nm and n = 1.26, respectively.
LBL-SA법을 이용한 고굴절률 ZrO<sub>2</sub> 박막 제조
최창식,이지선,이미재,이영진,전대우,안병조,김진호,Choi, Chang-Sik,Lee, Ji-Sun,Lee, Mi-Jai,Lee, Young-Jin,Jeon, Dae-Woo,Ahn, Byoung-Jo,Kim, Jin-Ho 한국전기전자재료학회 2017 전기전자재료학회논문지 Vol.30 No.4
$ZrO_2/PSS$ thin film with a high refractive index was fabricated on a glass substrate by a layer-by-layer self-assembly method. The surface morphology and thickness of the fabricated $ZrO_2/PSS$ thin films were measured as a function of the number of $(ZrO_2/PSS)n$. As the number of $(ZrO_2/PSS)n$ increased from n = 5 to n = 20, RMS roughness decreased from 29.01 nm to 8.368 nm. The $ZrO_2$ thin films exhibited high transmittance of 85% or more; and the 15-bilayer thin film exhibited the highest transmittance among the samples. The transmittance of the fabricated $(ZrO_2/PSS)_{15}$ thin film was ca. 90.8% in the visible range. The refractive index of the glass substrate coated by a $(ZrO_2/PSS)_{15}$ thin film with a thickness of 160 nm increased from ca. 1.52 to 1.74 at the 632 nm wavelength.
겹침이음실험을 통한 삼중나노소재 혼입 철근콘크리트보의 부착성능에 대한 실험적 고찰
유진규(Jin-Gue Ryu),손동희(Dong-Hee Son),배백일(Baek-Il Bae),유창기(Chang-Gi Yoo),최창식(Chang-Sik Choi) 대한건축학회 2023 대한건축학회논문집 Vol.39 No.10
This study aims to assess the impact of combining triple hybrid reinforced concrete with carbon nanotubes, nanosilica, and graphene oxide on bond strength. The mechanical properties of these materials were evaluated through material testing and assessed bond strength via lap-splice experiments. The material testing revealed that nano-reinforced concrete had a slight increase in compressive strength compared to regular concrete but showed a significant improvement in splitting tensile strength. It also exhibited decreased volumetric strain and Poissons ratio. To understand if these mechanical properties influenced bond strength, laboratory splice experiments were conducted using eight reinforced concrete specimens, varying splice length and cover thickness. The results of the lap-splice experiment showed variations in bond strength depending on the inclusion of nanomaterials in the mixture, with varying increases in bond strength as splice strength changed. This suggests that the combination of these triple nanomaterials does impact the bond performance of concrete.
최창식 ( Choi Chang-sik ),배백일 ( Bae Baek Il ),민경민 ( Min Kyung Min ),최현기 ( Choi Hyun Ki ),최윤철 ( Choi Yun Cheo ) 한국구조물진단유지관리공학회 2007 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.11 No.2
In remodeling projects, artificial openings will occur in wall section and this will degrade wall strength and stiffness. In this test, artificial damaged wall has been prestressed by tendons to improve wall shear capacity. And other wall have steel plate at the surface for the same purpose. Consequently, these retrofit walls show more capacity in shear and flexural. Especially, the wall with steel plate has shown ductile behavior after ultimate strength and prestressed wall have more stiffness in all the times of test rather than proto-type wall which have no retrofit.
최창식 ( Choi Chang-sik ),박영준 ( Park Young-jun ),김용현 ( Kim Yong-hyun ),최윤철 ( Choi Yun-cheul ) 한국구조물진단유지관리공학회 2007 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.11 No.2
According to the recent trends which conserve environment and make efficient utilization of resources in the construction projects, many structural engineers prefer to improve the deteriorated building capacity. So, a series of three shear wall specimens was tested under constant axial stress and reversed cyclic lateral load in order to evaluate behavior characteristics beam of coupling shear walls and slab of coupling shear wall. Specimens were 1/2-scale representations of two-story wall in a Korea apartment building that was built in 1980. The test of results, the ultimate strength of CW-RBS specimen and CW-RS specimen were 21.5% and 39.2% lower than that of original specimen. (Solid)
최창식 ( Choi Chang-sik ),최윤철 ( Choi Youn-cheul ),김현민 ( Kim Hyun-min ),최현기 ( Choi Hyun Kee ),이리형 ( Lee Li-hyung ) 한국구조물진단유지관리공학회 2006 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.10 No.1
Because of the characteristics relating to high tensile ductility, High Performance Fiber Reinforced Cementitious Composites (HPFRCC) are studied to be adopted in repair and retrofit of buildings. A series of three shear wall specimens was tested under constant axial stress and reversed cyclic lateral loading in order to evaluate the seismic retrofit that had been proposed for the shear wall with the opening. The retrofit involved the use of newly developed ECC and MDF(Macro Defect Free), both of which are sprayed through the high pressure pump, over the entire face of the wall. The results indicate that two difference types of retrofitting strategy make the different effects of a rise in the strength and ductility of each specimen.
최창식(Choi Chang-Sik),김경철(Kim Gyeng-Chul),김용일(Kim Yong-Il) 한국철도학회 1999 한국철도학회 학술발표대회논문집 Vol.- No.-
This paper studies on the benefit evaluation of urban railway construction project. We compares Korean Method with Japanese in calculating the generalized cost(GC) of a trip. In Japan, the disadvantage of transferring to another mode or line is included to calculate GC of trip. And environmental effects are contained directly as rail construction benefit. But in Korea, inconvenience of transferring facilities like stairways and passageway for riding a subway is not accounted to analyse benefit. As a result, there is a little investigate to improve and overcoming the inconvenience facilities of transfer, access, and egress. So, we suggest the containing the disadvantage measure of transferring facilities when subway riderships are forecasted. That will be reduced the capital size of subway.
유해대기오염 물질(HAPs) 유해대기오염물질의 정의 및 제반 규정
최창식 ( Chang Sik Choi ) 한국공업화학회 2016 공업화학전망 Vol.19 No.1
환경부에서는 배출구가 아닌 설비 및 공정 등에서 대기로 배출되는 유해대기오염물질(HAPs, Hazardous Air Pollutants)을 관리하기 위해 대기환경보전법 제38조 2항 규정에 따라 [비산배출 저감을 위한 시설관리기준] 제도를 2015.1.1.일부터 시행 중이다. 굴뚝이 아닌 생산공정이나 수송과정에서 배출되는 유해대기오염물질은 2012년도 기준 전체 배출량 5만 940톤의 60%를 차지하며 사회적 이슈로 대두되었고, 우선적으로 원유정제 처리업, 석유화학계 기초화학물질 제조업, 합성고무 제조업, 합성수지 및 기타 플라스틱물질 제조업, 제철업, 제강업 등 6개 업종을 대상으로 시행되었으며 2016.1.1.일부터 14개 업종이 추가되어 확대될 예정이다. 그 동안 국립환경과학원 등을 통해 대기모니터링, 유해화학물질 안전관리 및 HAPs 인벤토리 프로그램 구축 등 많은 조사와 연구 끝에 본 제도가 정착되었으며, 향후에도 비산배출 사업장으로부터 법규 만족을 위한 시설의 관리는 물론 지속적으로 더욱 효율적이고 경제성 있는 관련 분야의 기술 개발이 요구될 것이다. 본 고에서는 2015.08월 환경부에서 발간한 [비산배출 저감을 위한 시설관리기준 세부이행지침] 개정본이 방대하여 유해대기오염 관리대상 물질 및 제반 규정에 관하여 주요내용을 일부 발췌 편집하였다.